1. Field of the Invention
The present invention relates to a direct access storage device (DASD) and, more particularly, to improved electrical and mechanical structures and arrangements and enclosure assembly for a high performance small form-factor disk drive.
2. Description of the Prior Art
Computers often include auxiliary memory storage units having media on which data can be written and from which data can be read for later use. Disk drives incorporating stacked, commonly rotated rigid magnetic disks are used for storage of data in magnetic form on the disk surfaces. Data is recorded in radially spaced data information tracks arrayed on the surfaces of the disks. Transducer heads driven in a path toward and away from the drive axis write data to the disks and read data from the disks.
Disk drive dimensions are normally limited by a form factor, an industry standard of length, width and height dimensions. As disk drive device form factors become increasingly smaller, electrical connections to the using system can utilize an increasingly greater portion of the device form factor. In addition, the device interface and power connectors used, and the placement of these connectors within the device form factor results in industry standard elements. The resulting rigid industry standards provide significant geometric constraints on future models of a given product family or set.
Historically in small DASD's, 51/4" and smaller, a disk drive enclosure for a head/disk assembly (HDA) is fitted into a metal frame commonly called a user frame. This user frame is typically an aluminum die casting or formed from a sheet metal stamping. Generally, an HDA is attached to the user frame via three or four resilient vibration isolators or shock mounts. For these isolators to be effective, space is required between the HDA and the user frame to allow the HDA to move freely in response to external vibration or shocks. Threaded holes are provided at standard locations in the right and left sides and the bottom of the user frame for attaching the disk drive assembly to the using system box. Therefore, the user frame becomes firmly mounted to the using system box, but the HDA is both electrically and mechanically isolated via the vibration/shock isolators. When magneto-resistive (MR) heads are used within a file, electrical isolation is required between the HDA and the user frame. With smaller form factor disk drives, space constraints also restrict the use of resilient vibration isolators or shock mounts.
Other basic problems in a small form factor disk drive include space for electronics and the cost. When magneto-resistive (MR) heads are used within a file, a very low amplitude signal is provided so that amplification is required as early as possible in the electrical path to prevent picking up unwanted noise or causing signal degradation. The required amplifier circuits in the data channel, implemented by an integrated circuit, require external capacitors for tuning and noise filtering. With a small form factor, the surface area on the actuator available for supporting required arm electronics is limited. In known arrangements, components are mounted on a flex cable father away from the actuator. This conventional arrangement would adversely impact performance with the MR heads. Other known arrangements use expensive multi-layer ceramic or flex packaging to allow buried lines and vias. A need exists for a cost-effective, efficient and reliable packaging arrangement for arm electronics.
When magneto-resistive (MR) heads are used within a file, transducers and disks must be held at the same electrical potential. Known small form factor disk drives have provided a conductive path from the flex circuit to an actuator comb through a mounting screw. A need exists to provide a low cost manufacturable electrical path from the flex circuit to the comb.
Typically, electrical connectors have been registered in place by potting or gluing them into holes of the base casting plates. These approaches require a slow labor-intensive process in a clean room assembly to secure and seal the opening around the connector or require an additional connector on the inside of the disk enclosure. Often a data cable exits the disk enclosure to transmit read/write head signals to a card assembly on the outside of the disk enclosure. Typically the data cable extends along a smooth surface of the base and is squeezed between the surface and a rubber gasket. Extending from the device enclosure is a dangling data cable that is a source of damage during assembly and that does not lend itself well to automated assembly.
The spindle motor assembly is driven by signals from a card assembly on the outside of the disk enclosure. Typically a flex cable is used to carry signals to the spindle motor. This assembly process also is difficult to automate and susceptible to damage during assembly.
A mechanically stable enclosure structure is required for the disk drive. Mounting surfaces for spindle shafts, actuator shafts and actuator pole-pieces have normally been generated by a machining process for the disk enclosure (DE). The machining process is time consuming and expensive.
Magnetic disk drive assemblies require make-up air to compensate for small, slow leaks in the enclosure, and to adjust to environmental temperature and pressure changes. The components inside the drive are very sensitive to contaminants that can be easily introduced by an incoming air stream. These contaminants include small particles, organic vapors and inorganic gases containing ionic acids. All of these components may be present in the surrounding ambient air from which the make-up air is drawn.
Traditional filters have concentrated primarily on capturing particulates from the incoming make-up air. However, more recent designs have incorporated elements to remove the other components. The addition of filter elements for organics and inorganics requires additional space which becomes increasingly difficult to find as disk drive enclosures become smaller. The filter functions become separated into several stages, which are combined together either on top of, or alongside, one another.
Disk drive designs often incorporate a breather port to relieve pressure differentials and provide a controlled source of make-up air in the event of leakage. Breather filters provide filtration for particulates and, increasingly, for environmental chemicals such as plasticizers and corrodents. These filters commonly contain a high efficiency particulate air (HEPA) filter medium to remove particles from the air passing into the drive through the breather. A typical target efficiency for this media is 99.97% of particle .gtoreq.0.3 micron. A breather filter is designed to be the preferred point of entry of air into the drive and thus must have a low pressure drop; a typical specification is 0.1 in. of water at 30 cc/min. The relatively high pressure drop of HEPA media requires that a relatively large area be employed. The diameter for the media disk for small drive breather filters is commonly 10-25 mm. HEPA media used in such filters are either micro-fiber glass or expanded PTFE. Typical thickness of these is .ltoreq.0.5 mm. For chemical cleansing of the air entering the file, a layer of permeable chemically active media is placed in the breather directly upstream of the HEPA medium.
One known breather filter design disclosed in U.S. Pat. No. 5,030,260 has shown that the airflow path through the filter has a very significant impact on the performance and capacity of the elements which remove organics and acids. In that design, the geometry required to impart the proper airflow through the filter positioned the upstream and downstream diffusion paths alongside the filter chamber. This added greatly to the overall size of the filter. It also required a relatively large flat area for mounting.